Friday, October 15, 2010

Thermoelectric Power Plants Drink A Lot of Water

(this post is my contribution to's Blog Action Day 2010)

In the United States, thermoelectric power plants (coal, nuclear, natural gas) account for 48% (195 Bgal/d) of water use (U.S. Geological Survey, 2000). Now, 98% of this water is returned to the source, but the rest is lost to evaporation, and it's still a lot of unnecessary waste. You've seen those big, hourglass cooling towers spewing steam into the air? That's water being evaporated. Water that was taken from lakes, rivers, and estuaries. This is a tremendous waste of a precious resource. And the 98% that gets returned is hot water, so it causes lots of problems (see below).

And electricity generation by coal plants is typically only 30-49% efficient. So, for every watt you consume at home, more than three watts (for a 30% efficient plant, more than two for a 49% efficient plant) must be generated. The upside of this bad equation is that for every watt you conserve at home, you save two or three at the power plant, which also means you save water by a factor of two or three, too.

What to do? Put all those power hogging wall pack power supplies that provide power to your desktop pc peripherals (speakers, DSL/cable modems, external drives, printers, cameras) in a power strip, and turn the whole strip off when you're not using the devices. Those wall packs in standby mode (when the device is not in use) consume about 10% of electricity in the US. Unplugging them, or turning them off with a power strip will save that power. Same goes for home entertainment electronics -- dvd players, tv's, cable boxes, stereos, etc. -- plug 'em all into a power strip, and turn the strip off when you are not using those devices. They consume a ton of power in standby mode, too. Saving that energy would make a big dent in our global warming C02 output, and water consumption.

What else? Remember, every watt saved at home equals 2 or 3 saved at the power plant, and that much water, too. So...
  • Replace incandescent light bulbs with compact fluorescent bulbs -- they last much longer, and consume about 75% less electricity.
  • Turn the temperature up on your fridge and freezer a few degrees. This will save tons of power, and inconvenience you not at all. Also, turn off the "frost-free" option on your freezer -- it usually does no good (it is supposed to melt ice that forms in the freezer -- it rarely does), but wastes tons of electricity.
  • Turn the temperature up a few degrees on your air conditioner during the day, and turn it off entirely at night (open the windows and enjoy the sound of the crickets and breathe fresh, healthy, mold-free air for a change).
Keep in mind, there's a difference between water used and water consumed. Most power plants use a lot of water, but 98% of it is returned to it's source. The 2%, or so, is lost to evaporation in those cooling towers. Still, this water use creates lots of problems, and we don't have to use so much if we take some painless measures to conserve. Here's some discouraging water facts from Power Scorecard:

What are the consequences of water use and consumption?

Withdrawal of large volumes of surface water for either power plant cooling or hydropower generation can kill fish, larvae and other organisms trapped against intake structures (impinged), or swept up (entrained) in the flow through the different sections of a power plant.
Large fossil fuel and nuclear plants require incredible quantities of water for cooling and ongoing maintenance. The Salem Nuclear Generating Station alone takes 3 billion gallons a day from the Delaware Bay. Studies of the environmental consequences of this phenomenal water demand indicates that Salem is responsible for an annual 11 percent reduction in weakfish and 31 percent reduction in bay anchovy. At the Indian Point 2 and 3 reactors on the Hudson River, the number of fish impinged totaled over 1.5 million fish in 1987. The 90 power plants using once-through-cooling (see below) on the Great Lakes kill in excess of 40 million fish per year due to impingement (Pace University, Environmental Costs of Electricity, p. 287).
The use of water to generate power at hydropower facilities imposes unique, and by no means insignificant, ecological impacts. The diversion of water out of the river removes water for healthy in-stream ecosystems. Stretches below dams are often completely de-watered. Fluctuations in water flow from peaking operations create a "tidal effect," disrupting the downstream riparian community that supports its unique ecosystem. A dam's impoundment slows water flows, which hinders natural downstream migration of many fish species. By slowing river flows, dams also allow silt to collect on river and reservoir bottoms and bury fish spawning habitat. Silt trapped above dams accumulates heavy metals and other pollutants. Disrupting the natural flow of sediments in rivers also leads to erosion of riverbeds downstream of the dam and increases risks of floods.
The impoundment of water by hydropower facilities fundamentally reshapes the physical habitat from a riverine to an artificial pond community. This often eliminates native populations of fish and other wildlife. Dams also impede the upstream and downstream movement of fish and other wildlife, and prevent the flow of plants and nutrients. This impact is most significant on migratory fish, which are born in the river and must migrate downstream early in life to the ocean and then migrate upstream again to lay their eggs (or "spawn"). As mentioned above, withdrawal of water into turbines can also impinge or entrain significant numbers of fish.

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